Multi-tube annular heat exchanger



May 21, 1968 .1. R. HAYDEN MULII-TUBE ANNULAR HEAT EXCHANGER 5 SheetsSheet 1 Filed July 7, 1966 R I A INVENTOR. 06/72? 1? Hayden BY HTTOR'NE) May 21, 1968 J. R. HAYDEN MULTI-TUBE ANNULAR HEAT EXCHANGER 5 Sheets-Sheet Filed July 7, 1966 INVENTOR. A? @4162? cfdhv A TTOR/VE) y 21, 1963 .1. R. HAYDEN 3,384,166

MULTI-TUBE ANNULAR HEAT EXCHANGER Filed July '7, 1966 5 Sheets-Sheet 5 INVENTOR.

415/12? 1?; f/ayaezz Y United States Patent 3,384,166 MULTI-TUBE ANNULAR HEAT EXCHANGER John R. Hayden, Lockport, N.Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 7, 1966, Ser. No. 563,590 4 Claims. (Cl. 165-164) ABSTRACT OF THE DISCLOSURE A fluid heater to preheat combustion air by using hot gases such as engine combustion gases. The heater comprises inner and outer casing cylinders joined to coaxially arranged cylinders having stepped walls with the stepped walls being connected by arcuate tubes and the latter being separated by arcuate places in such a way that the fluids, such as air and gas, may flow countercurrently through the cylinders or tubes for optimum heat exchange efficiency accompanied by a minimum of structural expansion difliculties despite subjection to a wide variance in temperature.

A cylindrical heat exchanger for a hot gas reciprocating engine is disclosed in the United States Patent 3,015,475 granted Jan. 2, 1962 in the names of R. J. Meijer and M. L. Hermans. This patented heat exchanger includes multiple arcuate plates the surface areas of which move relatively about the axis of the exchanger, due to the tangential arrangement, when expansion and contraction of the metal occurs. Ribs relied upon to maintain radial spacing of the arcuate plates introduce considerable radial rigidity.

A toroidal heat exchanger utilizing plate tubes with exterior manifolding only is disclosed in the United States Patent 3,033,534 granted May 8, 1962 in the names of R. F. Caughill and F. A. Disinger.

An object of the present invention is to provide an improved heat exchanger sufficiently free of rigidity that expansion and contraction problems due to temperature changes are minimized.

To this end, a feature of the present invention pertains to coaxial cylinders having stepped walls connected by spaced arcuate tubes with baflle plates extending parallel with the tubes so that one fluid may flow along the lengths and outside the tubes and a second fluid may flow within the tubes.

These and other important features of the invention will now be described in detail in the specification and then set forth more particularly in the appended claims.

In the drawings:

FIGURE 1 is a sectional view through portions of a hot gas or external combustion engine on which a combustion air preheater of the present invention is installed;

FIGURE 2 is a sectional view looking in the direction of the arrows 22 in FIGURE 1;

FIGURE 3 is an enlarged sectional view looking in the direction of the arrows 33 in FIGURE 2 and omitting outer and inner casing and stepped plates and some of the tubes;

FIGURE 4 is a sectional view looking in the direction of the arrows 4-4 in FIGURE 3;

FIGURE 5 is a perspective view of the heat exchanger per se shown in FIGURE 1 with portions broken away; and

FIGURE 6 is an enlarged sectional view of a structural detail looking in the direction of the arrows 66 in FIG- URE 1 with tubes and spacer plates omitted.

The hot gas engine is not fully described herein as it is well known but it suffices to state that parts of such an engine are depicted in FIGURE 1. These parts include a displacer piston 10, a power piston 12, a regen- 3,384,166 Patented May 21, 1968 ice erator compartment 14, heat transfer fins 16, a cooler 18, heater tubes 22, a cylinder wall 24, a fuel atomizer 26, and an air preheater generally indicated at 28 supported between lower and upper insulator supports 30 and 32 and surrounding a burner arrangement 34.

The present invention is concerned with the preheater 28. Its use could be in other fields but, as disclosed in FIGURE 1, its function is to receive ambient air and heat it by means of heat exchange with engine exhaust gases for use in the burner arrangement 34 and also to serve as an insulator, both functions contributing to engine efficiency. The variations in temperature encountered in such a structure and use are great so stresses in the metal due to such variations must be avoided insofar as possible if preheater life is to be preserved. The present structure is extremely resilient both annularly and radially and therefore ofiers no expansion and contraction difliculties.

An annular air intake manifold 40 is partially defined by the support 30 and has an air inlet 42 and an annular air passage 44 blocked off by an annular series of triangular shoulders 46 but open to an annular series of triangular and upwardly directed ports 48. The shoulders 46 are inclined portions of a stepped wall cylinder 50 the bottom of which constitutes an annular flange 52. The ports 48 are defined by the steps in the cylinder 50 and the outer perimeter of a ring or base plate 54. Immediately above each shoulder 46 is a port 56 leading to the atmosphere and defined by the stepped cylinder 50 and an outer casing cylinder 58. The latter closely approaches the apices of the steps in the cylinder 50 and is firmly fixed to the flange 52. Alternating with the ports 56 are shoulders 60 formed from the cylinder 50 and integral with an upstanding flange 62. A ring or top plate 64 forms a part of the insulator support 32 and is fixed to the flange 62. From this, it may be seen that the steps in the cylinder 50 aid in forming flow passages A open at the top of the heat exchanger and closed at the bottom.

An inner casing cylinder 70 is supported at its top by being fixed to a flange 72 forming a part of the engine burner arrangement 34. Fixed to the top outer margin of the cylinder 70 is a flange 74 of an inner stepped cylinder 76 which cooperates with the inner casing cylinder 70 in defining vertical flow passages C open at the bottom to receive hot gas from ports 78 and closed at the top by shoulders 80. Alternating with the passages C are passages B partially defined by the inner stepped cylinder 76. The passages B are open at the top to com municate with the chamber 82 (FIGURE 1) and closed at the bottom by shoulders 84. The shoulders 84 and a flange 86 (FIGURE 5) are arranged to admit hot gas from the burner arrangement 34 to the heat exchanger.

A set of tubes 90 extends horizontally from each step in the stepped wall outer cylinder 50 and horizontally for about degrees around the axis of the exchanger to a step in the stepped inner cylinder 76. Holes 92 are drilled in each step to receive the ends of the tubes 90. The steps in the inner cylinder 76 are smaller than the steps in the outer cylinder 50 but, of course, of the same number in order to receive the tubes. The tube ends are easily brazed in place in the holes 92 to make leak proof joints. Each tube end is bent slightly more closely to achieve a normal approach to the supporting sheet metal and, hence, a better joint with the latter.

A thin impervious sheet 94 is retained between each of adjacent vertical sets of tubes 90 and each sheet 94 extends vertically from the bottom ring plate 54 to the top ring plate 64 and from near a vertical passage B and outwardly in an involute curve closely to approach a vertical passage D as best illustrated in FIGURE 2. Indentations or corrugations 96 are formed in the sheets 94 prior to assembly of the exchanger so that the tubes 90 are retained in properly spaced relation. The prime purpose of the sheets 94, however, is to serve as baffle means constraining gas flow outside the tubes to along the lengths of the tubes as will further appear.

When applied to a hot gas engine, air and engine exhaust gas are caused to flow countercurrently and in heat exchange relation. The flow of air before entering and after discharging from the tube nest is depicted by solid line arrows at the right side of FIGURE 1 and the flow of gas in the equivalent zone by dash line arrows at the left side of that figure. The air enters at 42, passes up into the series of vertical passages D, horizontally and along the outside of the tubes 90 as guided by the plates 94 and then upwardly from the passages B to the burner arrangement 34. The hot gas enters the bottoms of the vertical passages C, flows through the tubes 90 and then upwardly through the passages A and ports 56 to atmosphere.

The uncorrugated areas of the separator plates or sheets 94 are substantial so a radial range of movement of the tubes with respect to the heat exchanger axis is permissible, i.e., the tube and separator sheet arrangement is characterized by considerable resilience thereby avoiding stresses and strains which would otherwise develop.

I claim:

1. A heat exchanger comprising coaxially arranged cylinders defining an annular heat exchange zone between them, said cylinders having Walls with steps, said steps having surfaces facing in one direction around the axes of said cylinders and at an angle with the radii of the latter, parallel and spaced arcuate tubes extending through said zone partially around the axis of said cylinders and to the said surfaces of said walls, baflie means in said zone extending parallel with said tubes and adapted to prevent fluid flow transverse to the exterior of each of said tubes, annular baffle structure at each end of said exchanger defining an outer annular series of openings arranged at a given radius from the axes of said cylinders and an inner annular series of openings at a smaller radius,

and the arrangement being such that one fluid may enter through the outer series of openings at one end of the exchanger and flow along the exterior surfaces of said tubes to the inner series of openings at the other end of the exchanger and a second fluid may flow through the inner series of openings at said one end and inside the tubes to the outer series of openings at the said other end.

2. A heat exchanger as set forth in claim 1, the said surfaces each extending in a plane parallel with the axis of one of said cylinders and at an acute angle with the radius of the latter, and a set of said tubes having ends extending through one of said surfaces.

3. A heat exchanger as set forth in claim 1, an inner casing cylinder joined to the inside of one of said stepped wall cylinders, an outer casing cylinder joined to the outside of the other of said stepped Wall cylinders, and each step of said stepped Wall cylinders cooperating with one of said casing cylinders in defining a flow passage open at one end only of said heat exchanger.

4. A heat exchanger as set forth in claim 1, inner and outer casings joined to said stepped wall cylinders and defining flow passages, each of the latter being open at only one end of said heat exchanger, said tubes being divided into sets, and one side of each step of each stepped wall cylinder supporting open ends of one of said sets of said tubes.

References Cited UNITED STATES PATENTS 2,160,898 6/1939 Pefi 163 XR 2,479,071 8/ 1949' Henstridge 165163 3,231,016 1/1966 Stewart et al 165-164 3,280,899 10/1966 Brasie 16514O XR 3,282,257 11/1966 McInerney et al. 165-163 XR 3,285,326 11/1966 Wosika 165-4 ROBERT A. OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner. 

